Mobile radio installations for telephone traffic are characterized by transceiver base stations distributed over a given geographical territory and connected together by permanently established communication arrangements. When a call is made, temporary communication is established between these base stations and the mobile transceiver stations of the subscribers. In an extended version, these arrangements are not only used for speech communication but also for information transmission in general, in particular also for the transmission of data of any required kind. The requisite number of base stations and their location depend on the topographical features of the territory within which connections with subscribers are to be possible and on the number of such connections which can be established simultaneously. That being so, the criteria for the quality of service change constantly: in the short-term, as a result of variations in the volume of traffic and the change of location, in the medium-term through alterations to the landscape (buildings) and in the long-term through changes to the installation itself.
Modern installations cover extensive geographical territories and are run by many different undertakings--one example being the GSM or global European, digital, cellular mobile radio system. The operator of a mobile radio system requires dependable data on the service quality in his coverage area. Obtaining such data is both costly and time-consuming, as the quality of service depends on the particular location and traffic must be possible throughout the area which is covered.
CH-A-646294 describes a method and a device for testing traffic routes in a telecommunications network with permanent lines, by means of which the service quality of said network is investigated and can also be monitored, provided that the tests are performed often enough. In this case, a central unit controls a plurality of decentralized units distributed throughout the network by transmitting to the latter all the data necessary for a sequence of test calls via a modem dialling line. Thereafter, the decentralized units make calls automatically and store the test results which are then periodically consulted by the central unit. The traffic route testing permits the establishment of test calls between different points of the network; by doing so, it enables the situation regarding availability for the subscriber to be determined, in other words whether and after how long the subscriber obtains the dialling tone on request, whether and how long after dialling the ringing tone sounds, whether the line attenuation in both transmission devices fall within certain limits, whether the call charging is performed correctly, whether the line is correctly released after the connection has been terminated and so forth.
However, in the present instance of a mobile radio installation, there are no permanent lines to which decentralized units might be connected. In the case of a mobile radio system other parameters are of interest, such as position-dependent fluctuations in the receiving field strength, possible interference caused by more remote transmitters working on the same frequency, the behaviour on transition from one transmitting area to the next and so forth.
The brochure issued by the Alcatel SEL AG company of Stuttgart and entitled "Alcatel 900 Network Planning", Ed. 2, Feb. 1992, describes in its Chapter 3.2 (p 56-60) a system for the measurement and evaluation of radio connections in GSM networks. The system consists essentially of three parts: a measuring facility, to be installed on a vehicle, with a mobile test station which operates in compliance with the GSM recommendations, a conventional mobile telephone, a laptop computer and a positioning system, together with a base station simulator and an evaluation facility for cartographic presentation of the measurement results. The system assists the operator of GSM networks at different phases of development, in particular to determine the sites of the base antennas when the network is first set up. The base station simulator is used solely for that purpose. The mobile test station monitors the receiving field strength, the speech quality, various fault rates and the channel pulse response. It is connected via an RS 232 interface to the computer which controls the station and stores the values measured by it, together with the corresponding position data from the positioning system. The mobile telephone is operated in parallel with the test station. Its purpose is to correlate the subjective impression of speech quality with the fault rates. The stored data are saved onto diskettes for the stationary evaluation facility where they are loaded into the bulk memory of a powerful computer (workstation), processed and displayed together with pre-inputted cartographic information. By means of a colour-marked presentation of the measured values it is possible to visualize directly whether a base station site gives acceptable results.
The system as described is based on the continuous recording of measured values along selected routes. It requires a dedicated workplace in a vehicle and must be manned continuously. It is not able to supply relevant, large-scale data on the service quality of an operational mobile radio installation.